Study Of Manufacturing Methods And Laws Of Extrusion-based 3D Printing Of Zirconia/Nickel Functional Gradient Materials

Ceramic/metal functional gradient materials are a special type of non-homogeneous composite materials,which have been widely used in energy,aerospace,construction,agriculture,medical services,mechanical engineering and other fields because of their good resistance to high temperature,corrosion,high strength,light weight and high safety.However,due to the large difference in melting points and thermal expansion coefficients between ceramics and metallic materials,the current mainstream laser melting fabrication can make the material generate large residual thermal stresses during the preparation process,which can lead to problems such as shrinkage mismatch and interlayer cracking.Therefore,this paper proposes a new method for the preparation of ZrO₂/Ni functional gradient materials based on extrusion 3D printing,and improves the problem of internal stress caused by shrinkage mismatch between ceramics and metals through the shrinkage matching regulation of ZrO₂/Ni slurry,and realizes the preparation of high-performance ZrO₂/Ni functional gradient materials.In this paper,we mainly study the slurry blending,printing process,post-treatment process,and performance characterization,which provide a new method to solve the structural fabrication of ceramic/metal functional gradient materials and the high strength connection of ceramic/metal,and the main works are as follows:（1）Firstly,the relationship between the rheology and paste layer thickness of ZrO₂paste and Ni paste and the printing process parameters（printing air pressure,printing speed,printing height）were investigated,and the corresponding printing process windows were optimized.Then,by testing the thermal properties of the slurry and the properties of ZrO₂ and Ni materials with different solid contents under different post-treatment methods,the process parameters of the slurry degreasing stage and the influence of solid content and sintering temperature on the material properties were obtained:with the increase of solid content,the densities and mechanical properties of both ZrO₂ and Ni increased,while the shrinkage rate decreased;with the increase of sintering temperature,the densities and shrinkage rates of both As the sintering temperature increases,the densities and shrinkage of ZrO₂ and Ni both increase,while the mechanical properties increase and decrease respectively.Finally,by observing the macroscopic morphology and microstructure of ZrO₂ and Ni specimens,the mechanisms of solid content and sintering temperature on the material properties（densities,shrinkage,mechanical properties）were revealed,and the relationships between slurry,process and properties were established.（2）The ZrO₂ and Ni pastes used for gradient layer composite and their post-treatment methods were selected and validated based on the shrinkage matching principle and material properties,and the relationship between the layer thickness of composite pastes and printing process parameters was investigated.Subsequently,the composites with ZrO₂/Ni ratios of 25/75,50/50,75/25 were prepared and the effect of ZrO₂/Ni ratio on the material properties was investigated.Finally,the microstructure of the fracture of the composites was observed by SEM,and the preparation process of the transition layer of the functional gradient material was improved.（3）ZrO₂/Ni functional gradient materials with different gradient directions,different gradient layer numbers and different gradient layer thicknesses were designed and prepared,and then the effects of gradient layer numbers and gradient layer thicknesses on the deformation and mechanical properties of ZrO₂/Ni functional gradient materials were investigated by thermodynamic simulations and experiments,respectively.The results show that with the increase of the number of gradient layers and the thickness of gradient layers,the deformation of the material tends to increase,the deformation rate tends to decrease and then increase respectively,and the maximum deformation position of the material occurs at the corners of the model and the overall deformation trend is concave to the ZrO₂ layer.At the same time,the increase of the number of gradient layers and the thickness of gradient layers increases the strength and toughness of the material.Finally,the elemental distribution of the material section was characterized by EDS,and the Zr elements and Ni elements diffused evenly among the gradient layers with different proportions,and the elemental composition gradually transitioned from pure Ni to pure ZrO₂,so that the functional gradient material could have multiple properties and ensure the stability of its performance,and finally the ZrO₂/Ni functional gradient material with high structural integrity,good interlayer bonding and excellent performance was realized.The final result is the preparation of ZrO₂/Ni functional gradient materials with high structural integrity,good interlayer bonding and excellent properties.